Early wireless communication systems were developed to provide voice call services, supporting the activity of users. The fields of use for the wireless communication systems have extended to providing data services or high speed data services, beyond providing voice services.
FIG. 1 is a diagram showing a general wireless communication system. Referring to FIG. 1, the wireless communication system is capable of including user equipment (UE) 100, Radio Access Network (RAN) 130 and core network 140.
The RAN 130 may be divided into several entities: one of which is an entity 120 for interacting with the UE 100 through a wireless interface 110; and the others of which are entities connected to each other via wires in the wireless communication system. Examples of the entity 120 for interacting with the UE 100 through a wireless interface 110 are evolved Node B (eNB), Node B (NB) or Radio Network Subsystem (RNS) including NB, Base Transceiver Station (BTS) or Base Station Subsystem (BSS) including BTS, wireless access point, Home eNB, Home NB, Home eNB Gateway (GW), X2 GW, etc. In this description, for the sake of convenience, the term, radio access point, is called the RAN 130 or at least one of the examples of the entity 120, listed above.
Except for some exceptions, the radio access point 120 generally includes one or more cells each of which controls a specific range of coverage within which the UE 100 receives corresponding services. The cell refers to a cell of a general cellular system. The radio access point 120 refers to a device that manages and controls the cells. In this description, for the sake of convenience, the radio access point 120 may be used in the sense of ‘cell.’ In addition, when describing an object (e.g., embodiment), for the sake of convenience, the terms ‘cell’ and ‘radio access point 120’ may be used together.
The core network 140 is capable of including an RAN control entity 135. The RAN control entity 135 is in charge of general control functions, such as mobility management, authentication, security, etc. Examples of the RAN control entity 135 are Mobility Management Entity (MME), Serving GPRS Support Node (SGSN), etc. GPRS is short for General Packet Radio Service.
The radio access point 120 provides services to UE 100 through a wireless interface 110. To this end, each radio access point 120 has a proper range of coverage for providing services.
FIG. 2 is a diagram showing a case where one or more radio access points 120 have an overlapping coverage 220.
Two general radio access points 120a and 120b adjacent to each other have coverages 210a and 210b respectively. In this case, there may be an overlapping coverage 220 generated as the two coverages 210a and 210b are overlapped. When UE 100 receives services in the overlapping coverage 220, it may be susceptible to interference. For example, when UE 100 receives a service from a radio access point 120a in the overlapping coverage 220, it may be susceptible to interference by the radio access point 120b. 
The embodiment shown in FIG. 2 is implemented in such a way that the radio access points 120a and 120b have the coverages 210a and 210b similar in area to each other; however the present invention is not limited by the size of coverage. In addition, it will be appreciated that there may be various types of overlapping coverages where interference occurs, e.g., a case where the coverage 210a of the radio access point 120a is located within the coverage 210b of the radio access point 120b, a case where two or more overlapping coverages 220 are generated as the coverages of two or more radio access points 120 are overlapped, etc.
In addition to occurrence of interference, the overlapping coverage 220 may also cause frequent signaling. An example of the signaling is a handover-related signaling.
In order to resolve the problems, the 3rd Generation Partnership Project (3GPP) group has recently developed a technology for a number of radio access points 120 to make cooperative communication with each other. Examples of the cooperative communication technology are Coordinated Multi-Point Transmission and Reception (CoMP), Carrier Aggregation, etc.